Such services that interconnects different networks comprising a first network which includes, for example, a mobile network and a second network which includes, for example, a packet network or a next generation network (NGN), and allows terminals connected to the networks to exchange a moving image or a still image, have been already started. In these services, a gateway apparatus is used.
When communication is carried out between terminals using a moving image or a still image, compression/encoding of the moving image is performed on a terminal side in order to transmit it efficiently at a low bit rate. As a scheme for compression/encoding, ITU-T (International Telecommunication Union for Telecommunication Standardization sector) Recommendation H.263 and MPEG-4 (Moving Picture Experts Group Phase 4) internationally standardized by ISO/IEC (International Organization for Standardization/International Electro technical Commission) are known. In addition, H.264/MPEG-4 AVC (Advanced Video Coding), internationally standardized by ITU-T and ISO/IEC, compresses data more efficiently than the moving image compression/encoding schemes described above.
As a gateway that converts a moving image, Patent Document 1 discloses a gateway that converts moving image data, which is received from a server, using encoded parameters (encoding method, frame size, etc.) derived from a characteristic of a terminal to which the moving image data from the server is to be transmitted. As a configuration for extending temporal resolution, Patent Document 2 discloses a configuration in which the number of samples (frame rate) in a time-axis direction of a low-resolution moving image up-sampled, unwanted high-frequency components are eliminated, and a high-frequency prediction is made in the time-axis direction through non-linear prediction and, if the high-frequency prediction is correct, the temporal resolution is extended. As will be apparent from the description below, the present invention is absolutely different from the inventions described in those Patent Documents.
Patent Document 1: Japanese Patent Publication Kokai No. JP-P2001-313937A
Patent Document 2: Japanese Patent Publication Kokai No. JP-P2007-74307A